Method of induction heating of heat-treatable metallic workpieces and apparatus for performing same

ABSTRACT

The invention relates to a method of electric induction heating of heat treatable metallic work pieces steel articles and to apparatus for performing said heating.

United States Patent Nikonov et al.

[54] METHOD OF INDUCTION HEATING OF HEAT-TREATABLE METALLIC WORKPIECES AND APPARATUS FOR PERFORMING SAME [22] Filed: June 10, 1970 [21] App1.No.: 45,002

[30] Foreign Application Priority Data June 17, 1969 U.S.S.R. ..1336660 m"... g F 6 [151 3,684,854 [451 Aug. 15, 1972 [52] US. Cl. ..219/l0.69, 219/1057, 219/1071 [51] Int. Cl. ..H05b 5/00 [58] Field ofSearch ..2l9/10.69, 10.71, 10.57

[56] References Cited UNITED STATES PATENTS 2,476,935 7/1949 Wharff ..219/l0.69 3,083,285 3/ 1963 Haimbaugh ..2 l 9/ 10.69 2,439,517 4/1948 Johnson ..219/ 10.69 X 3,005,894 10/1961 Carbo et a1. ..219/10.69

Primary Examiner-R. F. Staubly Assistant Examiner1-1ugh D. Jaeger Attorney-Holman & Stern ABSTRACT The invention relates to a method of electric induction heating of heat treatable metallic work pieces steel articles and to apparatus for performing said heating.

2 Claims, 5 Drawing Ih'gures I llllllllrl METHOD OF INDUCTION HEATING OF HEAT- TREATABLE METALLIC WORKPIECES AND APPARATUS FOR PERFORMING SAME The invention resides primarily in a method of induction electric heating of workpieces for thermal treatment thereof, according to which each said work piece being heated is rotated about an axis extending at substantially right angles to the direction of the magnetic flux generated by the inductor effecting the heating.

The invention also resides in an apparatus capable of performing the above, characterized in that the electric current turns of the inductor structure lie in planes perpendicular the plane of rotation of the article being heated, some of these active electric current conductors of said inductor being disposed on one side from the plane of rotation of said article and being connected for electric current to flow therethrough in one direction, the other ones of the active electric current conductors of the inductor being disposed on the opposite side from the plane of rotation of said article and being connected for electric current to flow therethrough in another direction, opposite to the first direction.

The present invention relates to thermal treatment of metallic workpieces and, more particularly, it relates to a method of induction heating of steel components such as cross spiders for universal joints and to apparatus for performing such heating.

Uniform heating of a component to a desired optimal temperature for thermal treatment of the component is an important prerogative for good mechanical properties of the component after the treatment. When a component is treated, for instance, for a thermal hardening operation, both overheating and underheating of individual portions of the component can affect the mechanical properties of steel in these portions, whereby the quality of the component, as a whole, is affected.

For workpieces of intricate configuration electric induction heating is profitably employed, as part of their thermal treatment.

There is a known method of uniform electric induction heating of steel articles for hardening thereof, with the articles being rotated inside the inductor structure about an axis extending parallel to the magnetic flux.

However, some workpieces of intricate configuration, such as, for example, cross spiders for universal joints, cannot be uniformly heated by this known method, the reason being as follows. When an article of this kind is rotated about an axis extending parallel to the direction of the magnetic flux, the distribution of the electric currents induced in the article is substantially constant, and the density of these currents is greater in some portions of the article than in other portions thereof. In this case levelling of the temperatures throughout the article can take place only on account of the heat conductivity of the article, and this may prove to be insufficient for articles of intricate configuration.

It is an object of the present invention to provide a method of electric induction heating of heat treatable metallic workpieces and an apparatus for performing such heating, which ensures uniform heating of the entire structure of the component.

The present invention provides a method of electric induction heating of steel components of intricate configuration and an apparatus for performing such heating, which results in improved mechanical properties of the components after a hardening operation.

The method of the invention comprises the step of rotating each article being heated within an inductor structure, about an axis extending substantially at right angles to the direction of the magnetic flux generated by said inductor structure in operation thereof.

Preferably, the workpieces are rotated about axes perpendicular to the direction of the lines of the magnetic flux generated by said inductor structure in operation thereof.

The present invention further resides in an apparatus for performing heating by the above specified method, comprising a rotary table, a plurality of spindles mounted for rotation on said rotary table, each said spindle being adapted to carry thereon an article and to be rotated on its own axis together with said article, and a relatively stationary multi-coil inductor of a oncethrough type, wherein, in accordance with the present invention, the active electric current carrying conductors of said inductor extend in planes substantially perpendicular to the respective axes of said spindles, some of said active electric current carrying conductors of said inductor, disposed on one side from the plane of rotation of said articles, being electrically connected for electric current to flow therethrough in one direction, the other ones of said active electric current carrying conductors of said inductor, disposed on the opposite side from said plane of rotation, being connected for electric current to flow therethrough in another direction, opposite to said first direction.

The present invention will be better understood from the following details of a preferred embodiment thereof described with reference to the accompanying drawings, wherein:

FIG. 1 shows an apparatus for thermal treatment of steel cross spiders for universal joints;

FIG. 2 is a cross-sectional schematic view of an inductor structure and a cross spider placed within this inductor structure;

FIGS. 3 to 5 illustrate schematically the distribution of the electric currents induced in a cross spider rotated about an axis extending at substantially right angles to the direction of the flux of a magnetic field H.

Referring now in particular to the appended drawings, an apparatus for performing a method embodying the present invention comprises a framework 1 (FIG. 1) supporting thereon a rotary table 2 with a plurality of spindles 3 mounted for rotation on the rotary table 2 and uniformly circumferentially spaced therearound. The apparatus further comprises a stationary multi-coil inductor 4 of a once-through type, a cooling agent sprayer 5 and a mechanism 6 for removing articles off the spindles 6, operatively connected with a drive 7.

Steel cross spiders 8 for universal joints, which have to be heat treated are mounted one each on the successive spindles 3, whereafter the rotation of the table 2 brings these spindles 3 with the cross spiders carried thereby into the stationary inductor 4. Here the spindles 3 together with the cross spiders 8 are rotated about their respective axes I I (FIGS. 2 to 5). During a period when a spindle 3 with a cross spider 8 is carried by the rotation of the table 2 from the entrance of the inductor 4 to the exit therefrom, the cross spider is heated up from room temperature to a hardening temperature which is different for various articles, and, in case of-steel cross spiders for universal joints, can be from 830 to 850 C.

When a spindle 3 carrying a cross spider 8 leaves the inductor 4, its rotation about its axis is discontinued. After having passed the inductor 4, the spindles 3 with the cross spiders 8 carried thereby are introduced in succession by the rotation of the table 2 into the cooling agent sprayer 5, where the cross spiders are hardened, whereafter they are removed off the spindles by the mechanism 6.

Active electric-current conductors 9 (FIGS. I and 2) of the inductor 4 are disposed in planes perpendicular to the axes I I of the spindles 3. They surround the cross spider 8 mounted on the spindle 3 both from the side of the cross spider, facing the rotary table 2 i.e., from below) and from the opposite side of the cross spider (i.e. from above).

The spindle 3 and the cross spider 8 carried thereby are rotated about the axis of the spindle at a predetermined angular speed. Those of the current conductors 9 of the inductor 4, which are disposed on one side from the plane of rotation of the cross spider 8, have the electric current flowing therethrough in one direction (indicated with a symbol in (FIG. 2), whereas the rest of the current conductors 9, disposed on the opposite side from the plane of rotation of the cross spider, are connected for the electric current to flow therethrough in a direction opposite to the first one (indicated with a symbol in FIG. 2).

The inductor 4 of which the current conductors 9 are disposed as it has been described in the preceding paragraph, creates an alternating magnetic flux of which the lines H (indicated in FIG. 2) extend at substantially right angles to the axis of rotation of the cross spider 8.

It can be seen from FIGS. 3 to 5 of the accompanying drawings that when the cross spider 8 with its four projections 10, ll, 12 and 13 is rotated about the axis I l extending substantially at right angles to the direction H of the lines of the magnetic field, induction of the electric current which effects the heating of the projections 10, 1 1, 12 and 13 of the cross spider 8 takes place alternatingly in a magnetic field which, as far as each individual projection is concerned, now extends longitudinally relative to this projection, and then extends laterally relative to the same projection. The respective directions of the electric currents I induced in the cross spider 8 are indicated by curved arrow lines in FIGS. 3 to 5 of the accompanying drawings. Thus, when the cross spider is in a position illustrated in FIG. 3, the electric current I effecting the heating of the projection 10, is induced in a magnetic field directed longitudinally of the axis of the projection; in a position indicated in FIG. 5 the magnetic field is directed laterally of the projection 10, and in an intermediate position shown in FIG. 4 the magnetic field is directed at an acute angle to the axis of the projection. On the contrary, the projection 11 shown in FIG. 3 is heated by the electric current induced by the transverse magnetic field and in FIG. 5 by the longitudinal magnetic field. This shifting of the direction of the magnetic field relative to the axis of each projection 10, 11, I2 and I3 from longitudinal to lateral, and vice versa, brings about a cyclic redistribution of the electric currents induced in.the different portions ofthe article (i.e. of the cross spider in the herein described embodiment of the present invention), which provides a more uniform heating of the component.

Thus, when the cross spiders are rotated about'an axis extending substantially at right angles to the direction H of the magnetic field effecting the heating of these cross spiders, the latter are uniformly heated for a hardening operation, the temperature differential between various portions of the cross spiders not exceeding 20 C. This results in superior mechanical properties of the components after the hardening operation.

What is claimed is:

l. A method of electric induction heating of heat treatable metallic workpieces, comprising: conveying the workpieces in a first plane through an electric inductor to heat the workpieces; mounting each workpiece for rotation on its own axis substantially perpendicular to said first plane as the workpiece is conveyed through the inductor; and arranging electric coils of the inductor in such a manner that the direction of lines of magnetic flux produced by the electric coils in their operation is substantially perpendicular to the axis of rotation of each workpiece.

2. An apparatus for electric induction heating of steel components for thermal hardening thereof comprising: a rotary table mounted on a support structure and a driving means to rotate the table; a plurality of spindles mounted perpendicular to a plane of the rotary table for rotation about their respective axes, each said.

spindle being adapted to rotatingly support thereon a component to be heat treated; a relatively stationary electric inductor mounted on said support structure, the inductor comprising conductor coils with each turn disposed in a plane substantially parallel to the respective axes of said spindles, such that said components on the spindles are capable of being conveyed through the conductor coils of the inductor structure. 

1. A method of electric induction heating of heat treatable metallic workpieces, comprising: conveying the workpieces in a first plane through an electric inductor to heat the workpieces; mounting each workpiece for rotation on its own axis substantially perpendicular to said first plane as the workpiece is conveyed through the inductor; and arranging electric coils of the inductor in such a manner that the direction of lines of magnetic flux produced by the electric coils in their operation is substantially perpendicular to the axis of rotation of each workpiece.
 2. An apparatus for electric induction heating of steel components for thermal hardening thereof comprising: a rotary table mounted on a support structure and a driving means to rotate the table; a plurality of spindles mounted perpendicular to a plane of the rotary table for rotation about their respective axes, each said spindle being adapted to rotatingly support thereon a component to be heat treated; a relatively stationary electric inductor mounted on said support structure, the inductor comprising conductor coils with each turn disposed in a plane substantially parallel to the respective axes of said spindles, such that said components on the spindles are capable of being conveyed through the conductor coils of the inductor structure. 